There are a number of differences between these two types of currents.
First, surface currents affect much less water than thermohaline currents do. Surface currents can only affect about the top 400 meters of water in the ocean. By contrast, thermohaline currents move huge amounts of water -- more than 100 times the flow of the Amazon at any given time.
Second, surface currents are caused by winds and by the Coriolis Effect (having to do with the Earth's rotation). Thermohaline currents are caused by differences in the temperature and salinity of water in various areas of the oceans.
Thermohaline currents known as the currents of the ocean. It is specifically caused by variations in temperature and salt content. These two factors are two of the greatest forces behind the variation in water density, and different densities of water end up flowing in different directions. This creates a large loop of water circulation.
The water at the ocean surface is moved by winds that blow in certain patterns because of the earth,s spin and the coriolis effect. Winds are able to move the top 400 meters of the ocean creating surface ocean currents. Surface ocean currents form large circular patterns called gyres. Gyres flow clockwise in Northern Hemisphere oceans and counter clockwise in Southern Hemisphere oceans because of the coriolis effect.